The ruling comes after the Center for Biological Diversity argued that the one-mile test road made from phosphogypsum — a radioactive byproduct of fertilizer manufacturing — poses an unacceptable risk to public health. He added that the EPA’s decision does not violate Clean Water Act regulations, because the agency may approve applications for other uses of phosphogypsum and does not categorically prohibit the use of phosphogypsum in road construction. The fertilizer industry has argued using phosphogypsum in road construction would reduce the risk posed by the stacks.